This invention relates generally to subscriber carrier telephone systems, and more particularly concerns the adaptation of payphones to such systems.
Typical telephone carrier systems provide for frequency responses of from 200 to 3000Hz, thereby requiring all signaling to be accomplished by AC signaling methods. The use of inband signaling tones presents several inherent problems, among which are false signaling due to voice energy and user distraction due to auditory perception of the signaling tones. Typical signals include coin collect, coin return, coin present, dial tone, off-hook indication and ringing. Accordingly, the use of inband signaling has been considered as undesirable.